Workers in certain hazardous professions, such as emergency rescue workers and military personnel, may in certain circumstances be exposed to various chemicals, the inhalation of which can be irritating, health-threatening, or even life-threatening. Members of those professions have benefited from the development of a variety of air filter canisters designed to be used in conjunction with a protective breathing apparatus so as to reduce or eliminate specific chemicals of concern from breathable air, and thus limit or prevent inhalation of such chemicals.
Air filters have a finite capacity to effectively remove chemicals from breathable air, and consequently a single filter can adequately protect its user from a chemical threat for only a certain amount of time, after which it must be replaced with a new filter. The amount of time that a single filter remains effective is referred to as its service life. The effective service life of a filter is variable, depending on a number of factors, including the type of chemical it is designed to protect against, the concentration of the chemical to which it is exposed, the flow rate of air through the filter, and relative air humidity conditions.
Currently, the service life of a given air filter can generally be estimated only by manual reference to compiled data tables or by computer simulation. These methods have various drawbacks and disadvantages. For example, in the case of first responders in emergency or military situations, they are likely to be under extreme time pressure and must keep their hands free. In such cases, manual lookup tables can be bulky, confusing, and time consuming, while computer hardware is not always available and can be easily damaged.
Accordingly, there is a need for a device and method that can be used to quickly and conveniently estimate the service life of an air filter under various conditions.